Corrosion-inhibiting compositions

ABSTRACT

THIS INVENTION CONCERNS OIL-SOLUBLE CORROSION INHIBITING COMPOSITIONS COMPRISING AT LEAST ONE ANTI-CORROSIVE METAL SALT OF NAPHTHENIC OR AROMATIC TYPE ACIDS COMBINED WITH AT LEAST ONE OIL-SOLUBLE SURFACTANT HAVING AN HLB VALUE BETWEEN 1 AND 6. THESE COMPOSITIONS HAVE SUBSTANTIALLY GREATER CORROSION-INHIBITION PROPERTIES THAN DO THE ANTICORROSIVE SALTS THEMSELVES.

United States Patent 3,647,690 CORROSION-INHIBITING COMPOSITIONS EdwardA. Cross, Beaumont, Tex., assignor to Texaco Inc., New York, N.Y.

N0 Drawing. Filed Mar. 25, 1969, Ser. No. 810,345 Int. Cl. Cltlm 5/22US. Cl. 252-333 5 Claims ABSTRACT OF THE DISCLOSURE This inventionconcerns oil-soluble corrosion inhibiting compositions comprising atleast one anti-corrosive metal salt of naphthenic or aromatic type acidscombined with at least one oil-soluble surfactant having an HLB valuebetween 1 and 6. These compositions have substantially greatercorrosion-inhibition properties than do the anticorrosive saltsthemselves.

This invention concerns corrosion-inhibiting compositions and theirformulation in petroleum products.

More particularly, this invention relates to combinations of oil-solublemetal salts of naphthenic or aromatic type acids and oil-solublesurfactants which impart substantially improved corrosion inhibition topetroleum products than do the salts or surfactants used singly.

Metallic surfaces, particularly those containing ferrous metals requireprotection against corrosion. Not only does corrosion have an adverseeffect on the appearance and performance of metal surfaces but itreduces the operational life of the metal and necessitates expensive andunplanned repair or replacement. In addition, as in the case ofautomotive parts and many types of industrial machinery, vibration cancause the finely divided metal oxides to fall off and lodge themselvesbetween moving parts where they can function as abrasives. Further,inasmuch as automobiles and industrial mechanisms are frequently exposedto moisture and acidic products, it is well established to add corrosioninhibitors to lubricating formulations including greases and oils.

Corrosion inhibitors may be of the oil-soluble or watersoluble type. Thewater-soluble type is generally preferred for the protection of metalunder static conditions whereas the oil-soluble inhibitors are utilizedmore frequently for moving parts such as bearings where the grease filmis continually sheared and displaced.

Among the more Widely used anti-corrosives employed in lubricating oilsand greases are the oil-soluble metal salts of naphthenic and aromaticacids. Not only do these salts readily dissolve in the oleoginouslubricating stock, but they are relatively stable even at bothrelatively elevated and depressed temperatures. In addition these metalsalts are widely available in commercial quantities. Unfortunately, somemetal salts of naphthenic or aromatic type acids such as the alkalineearth metal sulfonates and heavy metal naphthenates are not highlyelfective when used alone even at relatively high concentrations. Thereis, therefore, a definite need for enhancing the effectiveness of therust and corrosion inhibiting properties of these salts by the use ofsmall quantities of additives.

Recently, during the course of exploratory work on increasing theeffectiveness of the metal salts of naphthenic and aromatic type acids,it was unexpectedly found that the addition of small quantities ofcertain oil-soluble surfactants to the metal salts of naphthenic oraromatic acid type inhibitors greatly enhances their efiicacy ascorrosion inhibitors and in some cases improves the water resistance ofthe grease or oil without any adverse effects. This is particularly truein greases of the lithium soap type. While the mechanism of how thisenhancement takes place is not fully understood at this time and nomechanism or "ice,

theory is relied upon for patentability, perhaps the following facts maybe useful.

While the structure of the useful surfactants vary, all show in common alow hydrophile-lipophile balance (HLB). HLB is the relativelysimultaneous attraction that the surfactant demonstrates for water andoil. Substances having a low HLB, from 0 to 12, are lipophilic andconsequently poorly hydrophilic. Thus the surfactants that enhance thecorrosion inhibiting properties of the metal salts of the aromatic typeacids, are strongly lipophilic and have little or no dispersability inwater. The HLB values of these surfactants can be calculated accordingto methods disclosed in various publications of the technicalliterature. See for example, Becher, Paul Emulsions: Theory andPractice, A.C.S. Monograph No. 162, p. 231, Reinhold PublishingCorporation, NY. (1965). However, for the purpose of classifying theuseful group of surfactants which potentiate the aforementioned classesof corrosion inhibitors, the following simplified classification system,based upon visual observation of the dispersibility of the surfactant inwater is employed.

Appearance: Visual 1 HLB value No dispcrsibility in Water 1-4 Poordispersion 3-6 Milky dispersion 6-8 Stable milky dispersion 10-13 Clearsolution 13+ 1 Based upon shaking about one part by weight of surfactantin ten parts by Weight of water for a period of five minutes.

Using the above visual scale, the favored surfactants have an HLB valuebetween 1 and 6, particularly when incorporated into lithium soapgreases.

To recapitulate, it is an object of this invention among others toenhance the effectiveness of metal salts of naphthenic or aromatic acidsas corrosion inhibitors in lubricating oils and greases.

It is a more specific object of this invention to provide novel lithiumsoap greases formulations with improved corrosion-resistance properties.

Another object of this invention is to improve the Water resistance ofgreases treated with the above described corrosion inhibitors withoutadversely affecting their other properties.

Other objects will suggest themselves to those skilled in the art aftera further reading of this application.

In practice, the above objects are achieved by incorporating into thegrease or lubricating oil to be protected, a corrosion inhibiting amountof a composition comprising:

1) At least one oil-soluble metal salt of naphthenic or aromatic typeacid selected from the group consisting of alkali metal salts, alkalineearth metal salts, heavy metal salts and their mixtures, and

(2) At least one oil-soluble surfactant having an HLB value betweenabout 1 and 6, then blending until a homogenous mixture is obtained.

In the preferred practice each parts by weight of the lubricating oilbase to be protected, containing 3 to 25 parts by weight of the lithiumsalt of fatty acid or acids as the thickener, is admixed with from about2 to 5 parts by weight of a corrosion inhibiting composition comprisingthe following components in the indicated proportions:

1) From two to ten parts by weight of at least one oil soluble metalsalt selected from the group consisting of lead naphthenate and alkalineearth metal dialkyl naphthalene sulfonates, and

(2) One part by weight of at least one oil-soluble surfactant having anHLB value between 1 and 6, then the admixture is heated with stirring toabout 200-230 F. for 15 minutes to 60 minutes or more, and milled to thedesired consistency.

In order to more clearly disclose the inventive concept, the followingadditional information is submitted:

(A) Oil-soluble metal salt of naphthenic or aromatic type acids-Thisterm as used throughout this application includes the oil-soluble,alkali metal, alkaline earth metal and heavy metal salts of substitutedcyclic or monoand diaromatic rings containing at least one acid groupsuch as -COH or -\SO H. Illustrative oil-soluble metal salts of theabove type include the lead, antimony, sodium, barium and calcium salts,among others. Specific compounds include lead naphthenate, antimonynaphthenate, sodium dinonyl naphthalene sulfonate, barium dinonylnaphthalene sulfonate, calcium octadecyl benzene sulfonate and calciumdinonyl naphthalene sulfonate, among others.

(B) Oil-soluble surfactant having a low HLB-These are oil-solublesurfactants derived from aliphatic mono and dibasic fatty acids andtheir derivatives and alkylated phenols, as well as their alkoxylatedderivatives, having an HLB value from about 1 to 6. The favoredsurfactants are selected from the group consisting of fatty acid estersof sorbitol, ethoxylated alkylated phenols, ethoxylated fatty acids,ethoxylated fatty amines, including diamines and monoamines, andethoxylated fatty amides, having the required HLB value, wherein thefatty moiety contains from 6 to 22 carbon atoms.

The preferred surfactants are the nonyl phenols ethoxylated with 2 molesof ethylene oxide, and the esters of oleic acid and sorbitol. Twopreferred surfactants and their HLB values appear below.

Surfactant: Approximate HLB values Sorbitol monooleate 4.5 Nonyl phenolpolyoxyalkylated with 2 moles ethylene oxide (C) Ratio of metal salt tosurfactant and what constitutes a corrosion-inhibiting amount.Theoil-soluble metal salt component of the corrosion-inhibiting compositionmust be present in excess compared to the oil-soluble surfactant. Aweight ratio of 2:1 to :1 represents the practical range of metal saltto surfactant, with 4:1 to 6:1 representing the range where the mostsignificant increase in anti-corrosive inhibition is obtained. For thisreason the latter, more narrow range (4:1 to 6:1) represents thepreferred weight ratio of the two components in the inventivecomposition.

In order to impart satisfactory corrosion inhibition to the greases andother petroleum products treated with the inventive compositions, it isnot only necessary to maintain the required ratio of the two componentsspecified supra, but in addition a certain minimal concentration of theanti-corrosive composition must be present. For some less stringentpurposes, it has been found that as little as 1:5% by weight ofanti-corrosive based on the total lubricant composition, represents acorrosion inhibiting amount as measured by the procedure of ASTM D-1743.However, to assure reproducible results, a concentration of at least 2%by weight of corrosion-inhibiting composition (based on the weight ofthe lubricant composition) is required. The upper concentration limit isa variable determined primarily by cost and the diluent effect thatlarger quantities of surfactant agents will have upon the physicalproperties of the lubricant. For most purposes this has been found to beabout a 5% by weight concentration and the preferred concentration rangetherefore is between about 2% to about 5% by weight of the two componentcomposition in the prescribed weight ratios.

(D) Lubricating oil base.The lubricating oils to be employed as themajor component of the corrosion-inhibited greases include any of thehydrophobic oils of lubricating viscosity derived from synthetic ornatural (petroleum) sources or their mixtures. The former include thealiphatic diesters such as bis-Z-ethylhexyl sebacate, bisdinonyladipate, alkyl mixed pentaerythritol esters, alkyl silicates,polyoxyalkylene monomers and their copolymers, alkyl silicanes, alkyland aryl phosphates such as trioctyl .4 phosphate, tributyl phosphate,tricresyl phosphate and the like.

The mineral or synthetic lubricating oils to be employed range upward inviscosity from about 50 SSU at F. The viscosity index of the oil canvary from below 0 to about 100 or higher and any mineral oil may behighly refined and/ or solvent treated.

The soaps utilized as the principal thickening or gelling agent for thegreases comprise the soaps of aliphatic hydroxy fatty acids ordinarilyhaving between about 10 and 30 carbon atoms, branched chain or straightchain. The preferred acids have between about 12 and 24 carbon atoms permolecule. These are typified by the acids derived by the saponificationof the hydrogenated castor oil acids principally 12-hydroxystearic acid.The glycerides, lower alkyl (methyl, ethyl) esters may be employed inthe saponification procedures. The soaps may be preformed but generallyit is convenient to form them in situ. The metallic portion of the soapsmay be monovalent (alkali metal), divalent (alkaline earth metal) orpolyvalent metal (lead or aluminum, etc.). The alkali metal soaps arepreferred, particularly the lithium soap of 12-hydroxystearic acid,referred to herein as lithium soap.

Ordinarily the metal soap is used in gelling amounts between 3-25 byweight of the base oil with 5-15 being a preferred amount.

(E) Test procedure for evaluating corrosion inhibitors.-The testprocedure used throughout this application this application to evaluatethe corrosion inhibition properties of the inventive compositions inASTM Designaton: D-1743-64 entitled Rust Preventive Properties ofLubricating Greases. The test is run twice, the duplicate run beingdesignated as check. In this procedure three clean new bearings arelubricated with the lubricant system to be evaluated, then run under alight thrust load for 60 seconds so as to distribute the lubricant in apattern that might be found in service. The bearings are thensubsequetnly stored for two weeks at 77 F. and 100 percent reltaivehumidity. After cleaning, the bearings are examined for evidence ofcorrosion and rated as follows according to the degree of corrosionfound. A hearing showing no corrosion is rated 1. Incipient corrosion nomore than three spots of a size to be visible to the naked eye is rated2. Anything more severe is rated 3 and considered as a failure. If theratings on two or three of the three bearings agree, this number isreported for the sam ple. If all three ratings are different, the testis repeated. For the purposes of this invention, to be consideredpassing, both the original and rerun (check) tests must give passingresults.

In order to present the invention in the greatest possible detail, thefollowing illustrative examples showing the preparation ofcorrosion-inhibited grease compositions and summarizing the resultsobtained in corrosion inhibition test are submitted.

EXAMPLE 1 Preparation of a corrosion-inhibited lithium grease A greasekettle equipped with heating, cooling and stirring means is charged with2225 parts by weight of a base grease containing 133.5 parts by weightof lithium -12-hydroxy stearate blended with 2091.5 parts by Weight of abase oil having the following properties: API Gravity 24.4; ViscositySUS at 100 F. and 84 SUS at 310 F.; Flash 450 F.; and Pour +20 F. Tothis base grease is added 45.4 parts by weight of a previously blended(210 F.) corrosion inhibitor composition comprising 45.4 parts by weightof a composition comprising 85.7 parts by weight of commercial leadnaphthenate and 14.3 parts by weight of sorbitan monooleate. (Thisrepresents a weight ratio of metal salt to surfactant of about 6:1). Thegrease containing the corrosion inhibitor composition is heated withstirring to 210220 F., is stirred at this temperature for 30 minutes,then milled using a colloid mill to grease consistency.

EXAMPLE 2-13 v pared using the procedure, order of addition, reactionPreparation and evaluation of other greases I temperatures, base oil,lithium soap and surfactant (sorbitol monooleate) of Example 1. The onlydifference is that in the P P P Order Of t q reaction the leadnaphthenate component is replaced on a weightconditlons described 111Example 1, corrosion-resistant and by.weight basis with the f ll isalts;

control greases are prepared using different combinations of leadnaphthenate and barium dinonyl naphthalene sul- Barium dinonylnaphthalene sulfonate fonate and different oil-soluble surfactants inweight ratios sodufm dmonyl naphthalene Sulfonate of approximately 6: 1.The results of evaluation of these Calcmm Octadecyl benzene Sulfonategreases and that of Example 1 are presented in Table I which follows.All parts are by weight.

In all these instances, satisfactory corrosion inhibition is obtainedwhen evaluated according to the procedure of ASTM D-l743-64.

TABLE I Example Number 1 2 3 4 5 6 7 8 9 10 11 12 Batch Number. 10141034 1063 1047 Composition, parts by Weight:

Lithium soap grease 100. 98. 0 98. 0 98. 0 98. 0

Lead naphthenate 2. O 1. 7

Barium dinonyl naphthalene sulfonate. 2. 0

Sorbitol monooleate polyoxyethylated th 6 moles ethylene oxide Sorbitolmonooleate polyoxyethylated with 20 moles ethylene oxide Nonyl phenolpolyoxyethylated with 2 moles ethylene oxide Nonyl phenolpolyoxyethylated with 6 moles ethylene oxide Nonyl phenolpolyoxyethylated with 30 moles ethylene oxide 0, 3 Approximate HLB value4 4 5 5 11 17 4 5 10 Rust test (ASTM D-1743-64 Overall rating Fall FallFall Fail Pass Pass Pass Fail Fail Pass Fail Fail Individual bearingratings 3,3,3 ,3,3 3,3, 3,3,3 1, ,1 1,3,1 1,1,1 3,3,1 3,3,1 1,3,1 3,3,32,3,3 Check rust test (D-1743-64):

Overall rating Fall P858 Fall Fail Pass Fall Pass Pass Pass Pass PassFail Individual bearing ratings 3,3,3 1,2,1 3,1,3 1,1,1 1,1,1 1,3,11,1,1 1,1,2 3,1,3 Water absorption, percent 50 20 25 25 20 50 80Penetration, original. 274 258 246 258 256 2&8 254 256 254 Emubion 30067 267 276 274 267 300 319 343 As can be seen from the data summarizedin Table I, As the specification, including the numerous examples,greases containing only the lithium base grease (Example 35 indicates,this invention offers several advantages com- 1) or the grease plus thelead naphthenate salt (Example pared to the prior art, for example, byutilizing the novel 2) or the grease plus barium dinonyl naphthalenesulformulations of this invention it is possible to increase fonate(Example 3) or the grease plus only the oil-soluble the corrosioninhibition of greases and lubricants protected surfactants (Example 4)fail to give adequate corrosion by the metal salt contained in theformulation. In addition, control. In contrast, Examples 5, 7 and 10,which utilize the oil-soluble, low HLB surfactants are low in cost andboth an anti-corrosive agent and an oil-soluble surfactant function atlow concentration levels. Two unexpected to protect the lithium basegrease, give satisfactory proaspects of the subject invention are (1)the gain in the tection against corrosion when the HLB value is betweenwater resistance of greases protected by both barium 1 and 6. Note thatnone of the grease compositions comdinonyl naphthalene sulfonate andsurfactant compared bining an anti-corrosive agent with an oil-solublesurto those protected by this metal salt alone, and (2) the factanthaving an HLB value above 6 provide the recorrosion resistance ofgreases protected by both comquired passing results in both the originaltest and the ponents of the corrosion-inhibiting system is substantiallycheck or rerun tests and therefore cannot be considered increasedcompared to the corrosion resistance of greases containing only one ofthe two components.

As the numerous examples demonstrate, various modifications, changes andsubstitutions in materials, reaction conditions and sequence of additioncan be made without departing from the inventive concept. The metes andas satisfactory anti-corrosive greases.

EXAMPLES 13-17 Preparation of different weight ratios of metal salt tosurfactant boun of thi inv ntio ar b st determ' aim 'Usmg the order ofaddmon reactlon conwhicl l follow reail in onimit'on 'th il 2 i i iizition drtlons, base oil (lithlum soap), metal salt and surfactant 0 l CJ 1 W1 pe described in Example 1, corrosion-inhibited greases are What15 1S1 prepared utilizing the same metal salt (lead naphthenate) Alubrlfiatlflg composltloll C tmg Of a and oil-soluble surfactant(sorbitan monooleate) but com- 1ubnat1ng 011 thlckened t0 coflslstem'fiybined in diflEerent weight ratios. The formulations are Wlth hthlumlz-hydfoxysteafflte d containing synergistic corrosion-inhibitingproportions of:

T bl 11. shown below m a e (a) one member selected from the groupconsisting of TABLE II lead naphthenate, barium dinonyl naphthalene sul-Example Number 13 14 15 16 17 fonate sodium dinonyl naphthalenesulfonate, and Lithium soap grease 97.2 97.5 97.6 97.75 97.8 calciumoctadecyl benzene sulfonate and ffiilti iftlifiiiai: 5:3 3:2 3:2 3'22313 one member h ving an HLB value between 1 and 6 selected from thegroup consisting of sorbitan In all instances, the above formulationsgave satismonooleate and nonyl phenol ethoxylated with two factorycorrosion-inhibiting properties when tested under moles of ethyleneoxide.

conditions specified in ASTM D-1743-64. 2. The grease of claim 1 wherein(a) is lead naphthen- X a I I ate. E PLE 18 3. The grease of claim 1wherein (a) is barium dinonyl Preparation of other corrosion-inhibitinggreases naphthalene sulfonata utlhzmg metal salts 4. The grease of claim1 wherein (a) is sodium dinonyl In this example, corrosion-inhibitinggreases are prenaphthalene sulfonate.

5. The grease of claim 1 wherein (a) is calcium octadecyl benzenesulfonate.

References Cited UNITED OTHER REFERENCES Polar-Type Riist Inhibitors by'Baker ef'all in Industrial and Engineering Chemistry, vol. 40, No. 12,

pp. 2338-2346. STATES PATENTS Fraser 252*36 5 DANIEL E. WYMAN, PrimaryExaminer Moore I. VAUGHN, Assistant Examiner Woods et a1. 25240 Sprouleet a1. 252-40 US. Cl. X.R. Panzer et a1. 252-332 10 25236, 41, 389

Greenwood et a1. 252-36 Scott 25236

